The present invention relates to a dry etching system for effecting dry etching with a semiconductor substrate having an aluminum film and a resist film provided on the aluminum film in a desired pattern so as to form an aluminum wiring and, more particularly, to a method of cleaning an etching chamber included in such a dry etching system.
A dry etching system etches an aluminum film or an aluminum alloy film masked by resist so as to form a wiring. It has been customary with the dry etching system to sequentially introduce semiconductor substrates, or wafers, into an etching chamber one by one. The problem with such a single wafer type dry etching system is that as the etching operation is repeated, products whose major component is the resist sequentially accumulate on the walls of the etching chamber. The products deposited on the walls of the etching chamber again evaporate and change the atmosphere in the chamber and discharge impedance, thereby critically lowering the reproductivity of the etching degree. For example, in a dry etching system having an etching end point detector, light issuing at the time of etching is prevented from being fully transmitted through a quartz window due to the products, preventing the detector from detecting the end of etching with accuracy.
In light of the above, it is a common practice to clean the etching chamber. In the single wafer type dry etching system, every time a hundred wafers are treated, oxygen gas is introduced into the etching chamber to generate plasma. The plasma effects dry etching in the etching chamber and thereby cleans the chamber. A cleaning method which cleans the etching chamber every time a single wafer is treated is also known in the art and distinguished from such a periodic cleaning method. The wafer-by-wafer cleaning method, directed toward a shorter cleaning time, is effected with a wafer left in the etching chamber or removed therefrom, depending on how the wafer is affixed to a stage.
However, both the periodic cleaning method and the wafer-by-wafer cleaning method need the same period of time in total, or the latter consumes a longer period of time than the latter. This reduces the throughput of the dry etching system. Further, assume that the wafer-by-wafer cleaning method is effected with a wafer left in the etching chamber. Then, even if treatment against aluminum corrosion is performed during the following plasma ashing, chlorine remains so long as the cleaning gas is implemented only by oxygen gas. As a result, when the wafer is exposed to the atmosphere afterwards, the remaining chlorine and moisture are coupled to turn out aluminum chloride. This causes corrosion to occur and degrades the reliability of wiring to a critical degree.